MP5990 and MP5991 eFuse SOA Curve Interpetation

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1

Hello,

I’m looking at the SOA curve for the MP5990 and MP5991 and have a question for my application. I plan to use this IC to control the 12V DC input into a device. The max DC current is around 35A for my application. When I look at the SOA curve on page 14 of the datasheet, the Ids limit seems to be set at 8A for the lowest Vds values. Once the 12V switch is activated, the rail should always be on. Am I interpreting this device incorrectly for my application. I guess the sloped Blue line in the plot is really what I should be paying attention to, but that’s in the 100s of mV range, not the 35mV I expect. Also, what does the 50A continuous current quoted in the datasheet mean if Vds on is typically in the tens of mV range. Any other comments would be appreciated and please let me know if I’m interpreting something incorrectly. It seems I need to double up on these parts for my application or use a external FET hot-swap controller.

Thanks,
Tony

2

Hello,

The SOA plot that you are starting at is the only the limit while the E-Fuse is in the linear region. This is not representative of the steady-state DC current limit once the switch is fully on.

50A is the continuous current limit that is a fully enhanced thermal rating. It coexists with Vds in the 10s of mV.

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The light blue line is the protection/SOA boundary to honor during both startup and faults.

3

For your 12V rail operating at 35A (double check on I2R loss and board thermals for your application), an MP5990 with a MP5991 pair should be sufficient for your purposes as shown:

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I would focus on the calculations on inrush and steady state thermal rise. Hope this provided some insight.

Best,

Krishan

4

Hi Krishan,

Thank you for the detailed response. I’ll review and see if this design works for our product.

Regards,

Tony